Nicotinamide adenosine dinucleotide NAD

The nicotinamide adenosine dinucleotide (NAD+) exits in anti- and syn-conformations ... 

Although the structures of ribavirin and selenazofiirin are similar, they appear to exert their antiviral action at different enzyme sites along the same biochemical pathway. Selenazofiirin forms the nicotinamide adenosine dinucleotide (NAD) analogue, which inhibits IMP dehydrogenase by binding in place of the NAD cofactor, and hence this potent reduction of guanylate pools is responsible for the antiviral effect of selenazofiirin. 

Arthur Harden and William J. Young (see chapter 1) showed three decades earlier that the fermentation enzyme in yeast is separable into a colloidal fraction ( zymase ) and a heat-stable, water-soluble fraction ( cozymase ). Tbe two fractions separately show no enzymatic activity. Warburg later demonstrated the activity of cozymase and, in 1936, nicotinic acid (niacin or vitamin Bj) was found to be its hydrolysis byproduct. In that year, Hans von Euler-Chelpin published the structure of nicotinamide adenosine dinucleotide (NAD ) and its phosphate derivative (NADP ) (see the structure below). Euler-Chelpin shared the 1929 Nobel Prize in chemistry with Arthur Harden for their independent studies on cozymase, seven years before publication of the NAD structure. In contrast to FMN and FAD, NAD, and NADP only transfer two electrons (H + 2e") at a time (see the structure below). 

The extreme selectivity of enzymatic reactions can be utiUzed best with enzymes catalysing electron exchange. Such enzymes are oxidases and dehydrogenases. The former catalyse redox reactions including oxygen [Eq. (7.21)], the latter such reactions with the participation of the coenzyme nicotinamide adenosine dinucleotide (NAD). Considering the oxidized form NAD" ", or the reduced form NADH, the general Eq. (7.22) is obtained ... 

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See also in sourсe #XX -- [ , , ]

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